The present invention relates to a new and improved construction of automatically engageable synchronous jaw clutch with hydraulic engagement-servo device.
With a state-of-the-art synchronous jaw clutch, as taught in German Pat. No. 1,181,992, and the corresponding U.S. Pat. No. 3,154,181 a respective toothed drive and power take-off clutch half and a clutch star are provided, the clutch star being guided to be axially displaceable by means of a first gear-tooth system upon one of the toothed clutch halves and can be engaged, by means of a second gear-tooth system, with the other clutch half. A screw socket controls, during clutching or engagement, the clutch star. This screw socket is in meshing engagement, by means of a pair of coarse-pitch thread means with one of the clutch halves and can be coupled, by means of a pawl blocking device, with the other clutch half. The engagement-servo device of the jaw clutch contains a piston which entrains the clutch star, and the displacement of the piston, initiated by the screw socket, controls an infeed channel leading to a servo cylinder chamber or compartment of the servo device, in order to hydraulically augment the engagement of the clutch. The screw socket is mounted to be axially non-displaceable in the clutch star and the piston is secured to a piston rod which, together with a head portion formed at its one end, likewise is mounted to be axially non-displaceable in the clutch star. The channel controlled by the piston extends through a fixed bushing in which there is guided the end portion of the piston rod which faces away from the head portion. This end portion has an annular groove at a spacing from the piston, this annular groove being continuously connected by bores with the cylinder compartment or chamber and, when the clutch is disengaged, does not flow communicate with the line controlled by the piston.
With this heretofore known clutch the clutching or engaging operation begins when the drive body, which is connected with a driving unit or machine, overtakes the power take-off body which is connected with a machine which should be driven. The overtaking phenomenon means that the clutch star temporarily leads, in relation to the screw socket, in the drive rotational direction, with the result that the pawl blocking device latches or engages, so that the screw socket is entrained in the drive rotational direction by the clutch star. Consequently, the screw socket carries out a relative rotation in relation to the power take-off body and the pair of coarse-pitch thread means insures that the screw socket carries out a screwing or threading motion towards the power take-off body. Since there is not possible any relative displacement of the screw socket in relation to the clutch star, the screw socket immediately entrains the clutch star in axial direction, whereby its second gear-tooth system begins to engage in the tooth gaps of the gear-tooth system of the power take-off body. In order to facilitate such both gear-tooth systems must be provided with helical portions. When such gear-tooth systems come into engagement with one another at a predetermined length, then the piston, which has been shifted in axial direction by the clutch star, reaches a position in which the channel controlled thereby is connected with the cylinder compartment. From this point on pressurized fluid medium flows without hinderance into the cylinder compartment and the pressure prevailing thereat displaces the piston and together therewith the clutch star further into the clutching or engagement direction, until the second gear-tooth system of the clutch star is completely coupled with the related gear-tooth system of the power take-off body.
The described known clutch has been found to be highly satisfactory even when working with large torques. However, if the clutch should be capable of transmitting extremely large rotational moments or torques, and thus, the clutch star must be dimensioned to be of a corresponding large size, then the moment of inertia of the clutch star can be so large that during a first phase of the engagement or clutching operation an appreciable torque must be transmitted by means of the clutch, in order to shift the clutch star in axial direction to such an extent until, during a second phase of the clutching or engagement operation, the axial force exerted by the pressurized fluid medium upon the piston and from such upon the clutch star, enables the clutch to completely engage. However, the rotational movement or torque required during the first phase, for instance when starting-up turbine-generator units, is not always available. On the other hand, the danger exists that the clutch star, at the end of the clutching operation, attains its end or terminal position, defined by stops, with too greater an axial velocity. Hence, owing to the large moment of inertia of the clutch star and the parts which are moved along their width, it is possible for damage to arise at the clutch itself and equally at the bearings of the shafts which are coupled by such clutch. With the heretofore known clutch it is possible to permit the piston, during the engagement operation, to displace the pressurized fluid medium into a second cylinder chamber or compartment, from where such pressurized fluid medium can outflow by means of a throttle location. However, it is difficult to regulate the throttling action such that it does not additionally render more difficult the incipient stage of the clutching or engagement operation of the clutch.